Processes of producing sugars and fermentation products, such as ethanol, from starch-containing materials are well-known in the art and used commercially today.
When producing fermentation products, such as ethanol, starch is conventionally converted into dextrins using a liquefying enzyme (e.g., Bacillus alpha-amylase) at temperatures above the initial gelatinization temperature of starch to above 100° C. The generated dextrins are hydrolyzed into sugars using a saccharifying enzyme (e.g., glucoamylase) and fermented into the desired fermentation product using a fermenting organism such as a yeast strain derived from Saccharomyces cerevisiae. Typically hydrolysis and fermentation are done in a simultaneous saccharification and fermentation (SSF) step.
Another type of process is also used commercially today. Starch is converted into dextrins at temperatures below the initial gelatinization temperature of starch and hydrolyzed into sugars during SSF. This type of process is referred to as a raw starch hydrolysis (RSH) process, or alternatively a “one-step process” or “no cook” process.
U.S. Pat. No. 4,514,496 concerns a process for producing alcohol by mixing a ground starchy material with mashing liquor without cooking, adding a saccharifying enzyme preparation derived from a Rhizopus sp., and adding an alcoholic fermenting yeast, and fermenting the slurry.
WO2003/066826 discloses a method for producing an alcohol by contacting a carbon substrate and at least one substrate-converting enzyme to produce an intermediate, and contacting said intermediate with at least one intermediate-converting enzyme.
WO 2004/080923 concerns a process for production of an alcohol product comprising the sequential steps of providing a slurry comprising water and granular starch; holding said slurry in the presence of an acid alpha-amylase and a glucoamylase at a temperature of 0° C. to 20° C. below the initial gelatinization temperature of said granular starch for a period of 5 minutes to 12 hours; holding said slurry in the presence of an acid alpha-amylase and a glucoamylase and a yeast at a temperature between 10° C. and 35° C. for a period of 20 to 250 hours to produce ethanol. A xylanase, cellulase and phytase may be present during the holding steps.
WO2004/081193 concerns a process for producing ethanol from plant material, comprising reducing the plant material to produce material comprising starch, saccharifying the starch, without cooking, with an enzyme composition, and fermenting the incubated starch to yield a composition comprising at least 15 vol-% ethanol.
WO2006/069289 concerns glucoamylases derived from Trametes cingulata, Pachykytospora papyracea, and Leucopaxillus giganteus and the use thereof in a process for producing a fermentation product from starch-containing material at a temperature below the initial gelatinization temperature.
WO 2011/068803 discloses glucoamylase derived from Gloeophyllum sepiarium, Gloeophyllum trabeum, or Gloeophyllum abietinum and the use thereof in processes of producing a fermentation product from starch-containing material.
The present invention is concerns enzyme compositions suitable for raw starch hydrolysis processes and the use of such enzyme compositions in such processes.